The present invention relates to smoking article wrappers and apparatus and methods for producing them. More specifically, it relates to cigarette wrappers which modify the burn rate of the cigarette and to an apparatus and method for efficiently producing such wrappers in commercial quantities.
It is beneficial to make cigarettes in commercial quantities which will have a reduced burn rate if not drawn on by the smoker but which look, feel, taste and burn like conventional cigarettes when being drawn on by the smoker at normal intervals. It is recognized by those skilled in the art that the wrapper configuration and construction strongly influences these characteristics.
Cigarette wrappers, i.e., papers, have known burn characteristics, including burn rates and static burn capabilities. There have been various attempts to modify the burn characteristics of such wrappers. These attempts have employed a variety of wrapper configurations and constructions.
For example, it is known that the burn characteristics can be modified by adding fillers and burn additives to the papers. Weinert U.S. Pat. No. 4,489,650 describes a cigarette in which the interior surface of the wrapper is coated with clay. In Cohn U.S. Pat. No. 4,044,778 the cigarette wrapper includes rings or areas coated with deposits from an alkali silicate solution which renders the wrapper non-burning in the coated areas. However, none of these wrappers produce cigarettes which look, feel, taste and burn like a conventional cigarette when being drawn on by the smoker at normal intervals.
Durocher U.S. Pat. No. 4,615,345 describes another attempt to modify the burn characteristics of wrappers. In that patent the wrapper was made of a cellulose fiber base which normally does not sustain combustion when the wrapper is incorporated into a cigarette. This type of wrapper was treated in selected zones with an alkali metal burn promoter such as the potassium salt of citric acid.
In addition to modifying wrapper burn characteristics by adding fillers and burn regulators directly to the base paper web, burn characteristics have been shown to be able to be modified by applying to the base paper web a strip or patch of a paper having different characteristics than the base web to be modified. For example, it is shown in co-pending, commonly-assigned U.S. patent application Ser. No. 07/777,466, filed Oct. 17, 1991, that cigarette paper can be modified by applying strips of a different paper at periodically spaced positions across the width of the paper web, so that cigarettes produced from the paper web have periodically spaced circumferential bands on the inside of the paper for modifying the burning characteristics of the paper and the cigarette. One treated paper material suitable for forming the periodically spaced strips is described in Hampl U.S. Pat. No. 4,739,775.
In addition to the various wrapper configurations and constructions discussed above for modifying the burn characteristics, there has been recent interest in providing apparatus and methods for implementing the various wrapper configurations in a commercially feasible manner. This interest is a result of the fact that although a proposed wrapper configuration may fulfill the necessary burn, look, feel and taste characteristics, the apparatus and methods used to produce them may be commercially inefficient. For example, in cigarette making machines where the wrapper is produced "on-line," the base paper web is moving at very high speed. Accordingly, if it is desired to place strips of paper on the web in order to modify the burn characteristics, it is difficult to control the placement of strips of paper on the web. More specifically, it is difficult to align the strips perpendicular to the edge of the base web edge as desired, or to provide the desired spacing between the strips. It also is difficult to assure that the strips are firmly adhered and set before they reach the garniture, so that they do not move during cigarette formation.
As discussed above, various types of cigarette wrapper configurations have been proposed for modifying the burn characteristics of cigarettes. However, these wrappers have various problems and disadvantages. Although the wrappers of Weinert and Cohn produce cigarettes with modified burn characteristics, they do not look, feel, taste and burn like conventional cigarettes. Although the wrappers of Durocher solve some of the problems exhibited by the Weinert and Cohn wrappers, Durocher did not disclose a process for making such cigarette wrappers in commercial quantities. Furthermore, although co-pending application 07/777,466, discloses a method and apparatus which can produce wrappers with both modified burn characteristics and which look, feel, taste and burn like a conventional cigarette when being drawn on by the smoker, such method and apparatus is not the only solution to the problems discussed.
Accordingly, it would be desirable to provide other cigarette wrapper configurations which overcome the problems discussed above. Furthermore, it would be desirable to be able to provide apparatus and methods that can efficiently produce such wrappers.